Language: match() enum-case subject must not match scalar int arms via backing coercion (Zend/zend_execute.c)

[PurHur]

Category

language · php-src-strict

Problem

Inverse of #9566 (scalar subject vs enum arm). When the match subject is an enum case object, arms labeled with backing scalars must not match via coercion.

Zend uses strict identity; match (F::X) { 1 => 'int_hit', F::X => 'case_hit' } returns case_hit.

This compiler coerces the subject to int and returns int_hit.

php-src reference

• php/php-src Zend/zend_execute.c — zend_match()
• php/php-src Zend/zend_enum.c — enum object identity
• Related: Language: backed enum strict compare with backing scalar — E::A === 1 must be false (Zend/zend_enum.c) #9546 strict === with scalars, Language: match() scalar subject must not match enum-case arms via backing coercion (Zend/zend_execute.c) #9566 scalar subject

Repro (failure today)

<?php
declare(strict_types=1);

enum F: int { case X = 1; }

echo match (F::X) {
    1 => 'int_hit',
    F::X => 'case_hit',
    default => 'miss',
}, "\n";

./script/docker-exec.sh php bin/vm.php test/repro-maintainer/match_enum_subject_scalar_arm.php
php test/repro-maintainer/match_enum_subject_scalar_arm.php

Engine	Output
Zend PHP 8.2+	case_hit
This compiler VM	int_hit

Scope

• lib/VM.php — match arm comparison (strict, no enum backing coercion)
• lib/JIT/ — match lowering shares compare helper with php-in-php: JIT SpaceshipCompareJit — route <=> through CompareJitHelper PHP not ~1.2k-line LLVM (#1492) #9476 SpaceshipCompareJit / enum guards
• test/compliance/cases/language/match_enum_subject_scalar_arm.phpt

Done when

• Repro prints case_hit on VM
• Pair with Language: match() scalar subject must not match enum-case arms via backing coercion (Zend/zend_execute.c) #9566 + Language: backed enum strict compare with backing scalar — E::A === 1 must be false (Zend/zend_enum.c) #9546 compliance suite green
• ./script/ci-fast.sh --filter match_enum_subject green

Related

• Language: match() scalar subject must not match enum-case arms via backing coercion (Zend/zend_execute.c) #9566 · Language: backed enum strict compare with backing scalar — E::A === 1 must be false (Zend/zend_enum.c) #9546 · php-in-php: JIT SpaceshipCompareJit — route <=> through CompareJitHelper PHP not ~1.2k-line LLVM (#1492) #9476 php-in-php compare JIT · Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492

[PurHur]

claim: worker-lane-c — starting this run

[PurHur]

Merged via #9783.

Status: Behavior already matched Zend on master — Variable::identicalTo() returns false for enum-case vs backing-scalar pairs (inverse of #9566). This run added the issue repro + VM/JIT compliance guards.

Verification:

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh
php bin/vm.php test/repro-maintainer/match_enum_subject_scalar_arm.php
php bin/jit.php test/repro-maintainer/match_enum_subject_scalar_arm.php
php vendor/bin/phpunit test/compliance/MatchVMTest.php --filter match_enum_subject_scalar_arm
php vendor/bin/phpunit test/compliance/MatchJITTest.php --filter match_enum_subject_scalar_arm
'

All output case_hit; PHPUnit OK (1 test each).